Pop music is usually considered to be brisk, chirpy and up-tempo radio fodder right? According to a recent report on music and culture however, that’s not altogether accurate.

The Washington Post reports that a recent study published in the Psychology of Aesthetics, Creativity and the Arts journal suggests that pop music has become progressively longer, slower and most importantly, sadder, increasingly conveying “mixed emotional cues.”

Conducted by psychologist E. Glenn Schellenberg and sociologist Christian von Scheve, the study analysed five decades worth of Top 40 hits taken from America’s Billboard charts to discover any shifting trends in the music. Taking their samples from “the mid-1960s through the first decade of the 2000s,” they discovered an “increasing percentage of pop songs are written using minor modes, which most listeners—including children—associate with gloom and despair.”

A crash course in music theory, songs in a major key (eg. Katrina & The Waves’ ‘Walking on Sunshine’) generally sound happier, while songs in a minor key (eg. Lana Del Rey’s ‘Videogames’) generally sound sadder. Sure, it’s all subjective, particularly when songs can flip-flop between modes, but according to the report, there’s been a dramatic increase in songs written in this more sombre mode.

Their research found that “the proportion of minor songs doubled over five decades,” with the increase starting around the end of the sixties, where 85% of songs that made it into the charts was written in a minor mode. As well as increase of popular songs being in a minor key, the researchers that the average tempo of songs had decreased overall, as well as a stronger correlation to sadder lyrical subject matter.

According to Schellenberg and von Scheve, “as the lyrics of popular music became more self-focused and negative over time, the music itself became sadder-sounding and more emotionally ambiguous.” While researchers pointed to “a general reduction in unambiguously happy-sounding recordings,” in direct contrast to “an increase in recordings with ambiguous emotional states.”

Additionally, they also found the percentage of female artists ranking chart hits rose steadily throughout the nineties before dropping off again at the turn of the century (something that Shirley Manson of Garbage recently noted with less scientific clout).

Researchers likened the pop music trend towards more emotionally ambiguous music with that of the shift in Classical music from 1600 to 1900. Speaking on the parallels in evolution, Schellenberg and von Scheve noted, “throughout the 17th and 18th centuries …. Pieces tended to sound unambiguously happy or sad. By the 1800s, and the middle of the Romantic era, tempo and mode cues were more likely to conflict,” namely allowing for greater musical expression.

“Popular music from 1965 to 2009 shows the same developmental trend over a much shorter time scale,” they added.

Surely there’s some questions over the validity of this research, such as the idea of what constitutes an “unambiguously happy” song, when music is a subjective experience. One person may find Lady Gaga to give them feelings of pop ecstasy, while for others it’s the very definition of musical hell (like Indonesia for example, where Gaga was recently forced to cancel a tour).